Destroyers.....

[Glider]

I agree with a lot of Parsifals last posting. Just some small detail about the pre war destroyers. All the A-I class destroyers had either 2 x 2pd or 2 x quad 0.5in mg's. Most of the Flotilla leaders had 5 x 4.7 instead of 4 x 4.7 but even these had the quad 0.5. These destroyers and the JKN/Tribal destroyers didn't have DP guns. They were SP guns only, if they had been DP why did the tribals have 2 x 4in instead of 2 x 4.7in?


The only RN Fleet destroyers with DP guns were the LM classes of which I think half had 6 x 4.7in DP and the rest 8 x 4in DP

During the war most if not all the A-I class ships were modified for convoy escort duties as new build destroyers came on line. Some of their guns and torpedos were removed and replaced by ASW weapons and some extra LAA gunds.

 

[RCAFson]

"No special prediction equipment was carried, which is a real giveaway about what the RN thought about their real AA potential>"

Or the mounting of a single 12pdr or 4 in gun on a high angle mount in place of one torpedo mount showed what was thought of the four-six 4.7 in guns on 40 degree mounts. And the 12pdr/4in was darn near useless. The ships would have been better served with a few single 2pdr or 20mm or even multiple .5 in MGs.

The special prediction gear (FKC, see: Fuze Keeping Clock - Wikipedia, the free encyclopedia ) wasn't ready till 1938, and then first priority went to the new destroyer classes and to the RN's new AA sloops which were fitted with HA 4in guns and the Hunt class destroyer escorts. By Dec 1941, some of the H-I class destroyers had been retrofitted with FKC AA FC, and with no war they might have all been retrofitted. A number of WW1 destroyers were also retrofitted with a full AA outfit and 2 x twin 4in HA mounts, but time and yard space didn't allow for all older destroyers to be retrofitted.

 

[RCAFson]

the JKN/Tribal destroyers didn't have DP guns. They were SP guns only, if they had been DP why did the tribals have 2 x 4in instead of 2 x 4.7in?

That's completely untrue. The 4.7in twin was a DP mounting, that had all the features required for AA computer control, including on on mount fuze setters, and the Tribal and later class destroyers used a dedicated AA director mounted just aft of the low angle director, which fed targetting info to the AA FC computer - see the schematic I posted earlier.

 

[Glider]

In theory it was a DP gun with all the trimmings but at the end of the day if you cannot get your gun to point at the target then all the director gear in the world will not help you.

As a result of combat experience all surviving Tribals had 2 x 4in installed and the last few had 8 x 4in not 8 x 4.7. All surviving JKN's had a 4in instead of a set of torpedo tubes.

You have to ask yourself why they felt the need to take such drastic action, if the 4.7in was a DP gun in the first place.

 

[RCAFson]

In theory it was a DP gun with all the trimmings but at the end of the day if you cannot get your gun to point at the target then all the director gear in the world will not help you.

As a result of combat experience all surviving Tribals had 2 x 4in installed and the last few had 8 x 4in not 8 x 4.7. All surviving JKN's had a 4in instead of a set of torpedo tubes.

You have to ask yourself why they felt the need to take such drastic action, if the 4.7in was a DP gun in the first place.

you have to realize that it wasn't until VT ammo came along that destroyers could engage aircraft with their main guns, at high elevation with a high probability of success, so a 40. 50 or 55 degree mount was not a huge drawback - because it was the CIWS that had the best probability of success against aircraft attacking a destroyer. The Tribal and later classes, opted to save weight by using a low angle DP main armament and use the weight saved to add a heavy CIWS, just as the USN Porter class used the weight saved to add 2 quad 1.1in mounts, however, unlike the Porter class the RN Tribals and JKM class also added a full AA FC system to their main armament. The plain fact is that destroyers needed more CIWS than they needed higher angle main armament, but large numbers of CIWS guns simply didn't exist, so HA 4in guns were added instead.

Here's an example of a USN Mk33 equipped destroyer trying to engage dive bombers at Eastern Solomons in Aug 1942:

Warren Armstrong, standing on the control officer's platform with his head out of his hatch, tried to coach the Mk-33 around to the diving planes. Jaworski and Serwitz would slew the director frantically by eye with their handwheels until, with Canaday's advice, they thought they were "on target," then would drop down to try to catch the plunging planes in their optics. It was an impossible task! At the rangekeeper, Copeland and I watched Warren's feet and lower torso expectantly as he squirmed about, hoping he'd get the director "locked on" to something so we could shoot. The attack was coming in from high over our section of the screen. The enemy planes were passing over our heads as they bore in on Enterprise. We'd whirl the director to try to get our sights on a Jap, but it takes a big arc of train to make even a small change near the zenith. They'd be over the top and out the other side before we could settle on them. Jaworski on the Pointer's scope reported "On Target" a couple of times, but he couldn't follow the fast motion as the attackers dove in. We never got a shot off!
http://destroyerhistory.org/goldplater/ussmaury/index.asp?r=40130&pid=40136

I find it hard to believe that Maury would have done any better in Norway in 1940, or at Crete in 1941 and she entered the war with a much lighter main armament with a much weaker CIWS than the Tribal and JKM classes.

 

[parsifal]

Im afraid I agree with glider on this one (and no, we are not conspiring against you RCAFson) . The article you posted from wiki includes some comments from Vian about the inneffectiveness of the 4.7" DP mount against aircraft. Not a complete waste of time, i will grant you, but not greatly effective either. As i recall Cunningham was similar in his view, though I cannot find at the minute his exact comments.

There were a number of problems with the 4.7" but more particularly its mount and support equipment. Some of these problems had little to do with the actual gun or the mounts. The RN adopted a faulty method of HA fire control for its medium and heavy batteries. i confess im not 100% certain of the specific types of directors used in given Destroyer classes, though I do know that the Battles were fitted with a "Mk VI" director and another apparatus called a "Mk XL corrector". However Campbell is pretty damning of all British pre-war direectors because of their methods of stabilization....in practice they proved incapable of dealing woith aircraft that were chamging course and or speed or altitude. they were better than nothing, but compared to the USN HA directors, were pretty average affairs.

For HA Short range weapponary, most work was done as over open sights until late in 1942. After that date , RN DDs began to receive some elementary beam switching gear. Dont ask me to give a detailed explanation, all I know is that it was linked to radars to give a pretty good indication of deflection and other corrections to the gunners of the LAA batteries. But in 1939, director control for the LAA in the RN was almost non existent.

The other problems with the 4.7 in mountings are squarely to with the gun and the mounts they were put into. The gun mounts, to put it mildly were simply too slow in both training speed and elevation to be effective, and as i suspected, the gun could not be loaded above 40 degrees elevation. The best turrets housing the 4.7 had a training sppeed of 10 degrees per secons and a max elevating speed that was the same. by comparison, the 4.5s in the battles were nearly twice that speed. The USN 5/38 had a traverse speed of 34 degreees per second and and elevating speed of 18 degrees per second. put simply the 4.7 was too slow to be effective, and wasnt well directed until later in the war

 

[Glider]

The Porters had weight problems as they tried to include eight main guns and a full set of torpedos. The Tribals didn't have such a problem as they lost a set of torpedos in the design stage. Don't confude the two. Also the weight of the quad 2pd was about the same as two quad 1.1in mounts.
The Porters didn't have DP guns as that would had pushed the weght further, The Tribals because the RN didn't fit DP guns in DD's at the time.

Switching a twin 4in for a twin 4.7 had nothing to do with weight.

 

[RCAFson]

Im afraid I agree with glider on this one (and no, we are not conspiring against you RCAFson) . The article you posted from wiki includes some comments from Vian about the inneffectiveness of the 4.7" DP mount against aircraft. Not a complete waste of time, i will grant you, but not greatly effective either. As i recall Cunningham was similar in his view, though I cannot find at the minute his exact comments.

There were a number of problems with the 4.7" but more particularly its mount and support equipment. Some of these problems had little to do with the actual gun or the mounts. The RN adopted a faulty method of HA fire control for its medium and heavy batteries. i confess im not 100% certain of the specific types of directors used in given Destroyer classes, though I do know that the Battles were fitted with a "Mk VI" director and another apparatus called a "Mk XL corrector". However Campbell is pretty damning of all British pre-war direectors because of their methods of stabilization....in practice they proved incapable of dealing woith aircraft that were chamging course and or speed or altitude. they were better than nothing, but compared to the USN HA directors, were pretty average affairs.

For HA Short range weapponary, most work was done as over open sights until late in 1942. After that date , RN DDs began to receive some elementary beam switching gear. Dont ask me to give a detailed explanation, all I know is that it was linked to radars to give a pretty good indication of deflection and other corrections to the gunners of the LAA batteries. But in 1939, director control for the LAA in the RN was almost non existent.

The other problems with the 4.7 in mountings are squarely to with the gun and the mounts they were put into. The gun mounts, to put it mildly were simply too slow in both training speed and elevation to be effective, and as i suspected, the gun could not be loaded above 40 degrees elevation. The best turrets housing the 4.7 had a training sppeed of 10 degrees per secons and a max elevating speed that was the same. by comparison, the 4.5s in the battles were nearly twice that speed. The USN 5/38 had a traverse speed of 34 degreees per second and and elevating speed of 18 degrees per second. put simply the 4.7 was too slow to be effective, and wasnt well directed until later in the war

Vian states that AA fire from 4.7in guns prevented a single hit from an attack lasting many hours, on a whole convoy moving at 5 knots, through narrow waters - if RN destroyer AA was so ineffective why didn't the bombers press in to low altitude and annihilate the convoy? What was the luftwaffe afraid of? Do you really think that USS Maury could have done any better? Mk 37 wasn't even service in April 1940, and the Mk 33 system on Maury and most of the prewar USN destroyers was an obvious failure as the USN itself admitted.

I have a feeling that the effectiveness of USN AA systems has been greatly exaggerated and this has given the impression that if only the RN had similar systems that all would have been well...yet a read of the two volumes of First Team, will show you that USN AA simply didn't do well and was hardly a factor in the first year of the war, until Santa Cruz, and then it was massed CIWS fire that proved effective, not 5in Mk 37 fire.

I think XL means "cross level" as GXLC means "Gyro cross level corrector" and Campbell states that it was part of the director, not a separate unit. Cross level correction was only really important at very high angles while firing far forward of the beam, and so was not an issue for Tribal class AA although there was a cross level corrector in the LA firing circuit.

No WW2 AA system could deal with aircraft that were changing course or speed and/or changing altitude since all WW2 AA computers could only predict straight-line target motion, and assumed that the target would fly at a steady speed during the prediction cycle. Mk37 could predict motion based upon a steady rate of climb or descent, but only if the target flew level in a straight line at a steady speed. As for 10degs/second traverse, it was plenty to track low elevation targets:

A 270 knot (500 km/h) target crossing the line of sight at right angles, at 2000 yards (1829 m) range, will move across the line of sight at 4.5 degrees per second. This simple fact of geometry appears to contradict the assertion that a 10-degree-per-second traverse rate was too slow to track a high-speed aircraft.

Higher speeds were only needed against very close range targets ( AFAIK higher speeds are only needed to engage dive bombers that are nearly directly over the ship) but the AA computers, including MK 37 were not effective at such high angles anyways because they were to slow to compute the needed corrections, and MK 37 was not accurate above 70 degs due to it mechanical limits:
Historic Naval Ships Visitors Guide - Computer Mark 1 and Mark 1A
http://www.hnsa.org/doc/computermk1/pg380.htm
After the war electrical computers could do much better.

Beam switching refers to a method of getting accurate bearing information from a radar; the radar beam is switched rapidly between the left and right sides of the antennae and if the radar antennae is not centered on the target, the target will flicker on the display tube. After 1942 beam switching was introduced on type 285 and type 282 radar.

Most RN destroyers used eye shooting for CIWS AA until late war when the Simple Tachymeyric Director ( similar to Mk 51) began to be fitted to some destroyers to control CIWS guns, and some pom-poms were fitted with gyro gunsights similar to the USN Mk 14. USN destroyers began to receive Mk 51 in 1943 to control twin bofors mounts, although the RN Hazemeyer was theoretically far more accurate, it was not very reliable. Almost all RN cruisers and larger ships had director control of pom-pom mounts starting around 1930, where the USN didn't have director control of 1.1in or Bofors guns until 1942.

The USN admitted that MK 33 was a very poor director:

The USN never considered the Mk 33 to be a satisfactory system, but wartime production problems, and the added weight and space requirements of the Mk 37 precluded phasing out the Mk 33: "Although superior to older equipment, the computing mechanisms within the range keeper (Mk10) were too slow, both in reaching initial solutions on first picking up a target and in accommodating frequent changes in solution caused by target maneuvers. The Mk 33 was thus distinctly inadequate, as indicated to some observers in simulated air attack exercises prior to hostilities. However, final recognition of the seriousness of the deficiency and initiation of replacement plans were delayed by the below decks space difficulty, mentioned in connection with the Mk28 replacement. Furthermore, priorities of replacements of older and less effective director systems in the crowded wartime production program were responsible for the fact the Mk 33's service was lengthened to the cessation of hostilities."[19]
Ship gun fire-control system - Wikipedia, the free encyclopedia

and:
From the "Sham battles" we had with our own carrier planes, it became clear that in war we would be subjected to attacks which broke very quickly, seldom with any warning. When an incoming plane was sighted, we would struggle to get our director's sights on target, measure the rapidly closing range, adjust the Mk-10 to a solution and simulate opening fire before the attacker could complete his attack. Frequently we'd still be "slewing" the director to get on target when he roared overhead, attack completed. We held tracking drills at every opportunity to improve our ability to acquire targets quickly, but we had no mechanism to point out the target to the men on the director's telescopes—the control officer had to coax them on by voice. I became seriously concerned that we couldn't handle incoming dive or strafing attacks.
http://destroyerhistory.org/goldplater/ussmaury/index.asp?r=40130&pid=40131 (the MK 33 director contained a Mk 10 rangekeeper (computer) )

but one would never know about these problems by reading Campbell because he glosses over defects in the USN AA firecontrol, while being highly critical of less serious problems in RN AA fire control.

 

[RCAFson]

The Porters had weight problems as they tried to include eight main guns and a full set of torpedos. The Tribals didn't have such a problem as they lost a set of torpedos in the design stage. Don't confude the two. Also the weight of the quad 2pd was about the same as two quad 1.1in mounts.
The Porters didn't have DP guns as that would had pushed the weght further, The Tribals because the RN didn't fit DP guns in DD's at the time.

Switching a twin 4in for a twin 4.7 had nothing to do with weight.

The Tribals had DP 4.7in guns controlled by an AA FC computer but if HA guns were so important why didn't the Porter/Somers class have their LA guns replaced later in the war?

The RN didn't want to reduce the gun armament of their destroyers, so they were willing to add guns in lieu of torpedo tubes, but they weren't willing to reduce torpedos to nil, and so on the Tribals they opted to keep the torpedoes and replace a twin 4.7in with a twin 4in (while saving 9 tons of topweight). Adding a 2nd pom-pom would have meant removing all torpedoes or reducing gunpower by by 25%.

 

[Glider]

They did. At the end of the war Porters and Sommers were normally equipped with 4 x 5in (2 x 2) 1 x 5in DP in X turret. 6 x 40mm 8 x 20mm and 8 x TT
It varied a little but B and X turrets were removed to add LAA and the single DP 5in reinstalled in X. It should be noted that some books refer to these vessels as having DP guns from the start but they didn't. The Mk22 mount only had a 35 degree elevation. To save topweight they also lost a director, a deck in bridge height, lowered funnels, lighter masts, a set of torpedos from the Sommers, plus of course the two turrets.

In brief the USN vessels were top heavy before the war started. The Tribals didn't, they started the war with eight main guns and finished the war with eight main guns. They were able to absorb the war changes with little difficulty because they were a more balanced design from the start.

I am afraid I don't understand your comment about the adding a quad 2pd at the cost of 25% of the guns. They started the war with one quad and finished with one quad 2pd. Had the Tribal spent most of the war in the pacific I have little doubt that the AA fire would have been changed. Quite probably to a similar level as the last Canadian built Tribals 8 x 4in DP, 6 x 40mm, 4 x 20mm and 4 x TT which are a better balance than the Porters

 

[vinnye]

I believe the 25 % reduction in gun armament is achieved by removing a pair of 4.7 inch making a total of 6 still fitted - a 25 % reduction from the 8 originally fitted.
The removed turret gives space for adding a quad.

 

[stug3]

Officers on the bridge of a destroyer, escorting a large convoy of ships keep a sharp look out for attacking enemy submarines during the Battle of the Atlantic.

A photograph taken from the bridge of HMS VISCOUNT which gives a good idea of the difficult weather conditions while escorting a convoy during the Battle of the Atlantic. During this operation HMS VISCOUNT and HMS FAME rammed and sank two German U-boats.

 

[parsifal]

Higher speeds were only needed against very close range targets

No incorrect. Slower travers speeds mean the mount spends more time moving, and less time firing, and when you have second in which to respond that can be critical. A turret capable of traversing at 10 degrees per second can move through an arc 650m every second at a radius of 4000m. in that time an aircraft traveling at 250 miles can move about 150m every second. If the destroyer is being attacked from head on and beam on simultaneously, and if we allow say 5 secs for orders to change targets thats a delay of say 8-10 secs before the guns can be pointed at the initial position of the target aircraft,. however if the target is moving in an arcing movement toward another target, say abaft the Destroyer, then by the time the aircraft will have reduced the range to target by about 1500m in the time it took that DD to move its turrets in the general direction of the target a/c. But now, 8 secs later, the range is down to 2500m (assuming equidistance between the DD and the aircraft, and the a/c target and the aircraft). At that point the DD turrets can arc through only 438m per sec @ range 2500m while it is traversing.....effectively it is now losing 25% of its ROF because 1 in 4 seconds the turret has to move rathe than fire . and this situations just gets worse as the range drops. However even more serious is the loss in enagement time. If the effective torpedo launch range is 2000m the gun now has only 4 secs in which to find a firing solution and fire. assuming it can fire immediately, it might get off 0.7 rounds if its lucky. Effectively thats just one round before launch.....

Now, applying that same battle situation to a US 5/38 mount....it has a traverse rate of 34 degrees per second and an effective rof of around 20 rpm. In that same situation its guns can be moved to the new target in in 6 secs, That places the tartget a/c at a range of about 3000m from the firing gun, and also about 3000m from the target ship (remamber, for simplicity I have assumed equal distances). At 3000m the target a/c has 8-10 before it can launch. The 5/38 only loses another second in that time for traverse adjustments, meaning it has 7-9 secs of firing time. theoretically that means it could get up to three rounds off in that time.

Effectively, in that situation, disaregarding all the other gizmos and paraphenalia (I can never spell that word), the 5/38 is three times as effective as the 4.7 gun simply because of its better rof and higher traverse speed.

Traverse speed is a bit like a bombers best speed. Every bit counts. in the case of the bomber, even though it cannot outrun a fighter, every ounce of speed is still importance because of endurance issues. For the AA gun traverse speed is actually critical, because it has only seconds to respond, and every second lost traversing is less lead in the air. and in the end, thats what counts.

 

[Shortround6]

traverse and elevation speed also get used up compensating for the destroyer's ( or ship mounted on) motion. In this case traverse and elevation acceleration are important but they tend to be somewhat proportional to traverse and elevation speed. Mounts with faster speeds have faster acceleration.

 

[RCAFson]

I am afraid I don't understand your comment about the adding a quad 2pd at the cost of 25% of the guns. They started the war with one quad and finished with one quad 2pd. Had the Tribal spent most of the war in the pacific I have little doubt that the AA fire would have been changed. Quite probably to a similar level as the last Canadian built Tribals 8 x 4in DP, 6 x 40mm, 4 x 20mm and 4 x TT which are a better balance than the Porters

Many Tribal class did serve in the Pacific (all the RAN ones), but the point is that adding a quad pom-pom either means removing the only TTs or reducing gun power by 25%. The solution was to swap a 4.7in twin for a 4in twin. The last Canadian built Tribals had 6 x 4.7 and 2 x 4in, as did all the wartime Tribals, and unlike the Porters' 5in they could use their 4.7in in controlled fire, giving them a heavy AA armament.

 

[RCAFson]

No incorrect. Slower travers speeds mean the mount spends more time moving, and less time firing...

It certainly is possible to create scenarios where high traverse rates are useful, but typical AA engagements involve picking the aircraft up when it was still considerable ways from the target, and usually before the point where it has to steady on it's bomb run, and 10degs/sec is quite adequate for that. This was especially true after radar became widespread in 1941.

 

[Glider]

Many Tribal class did serve in the Pacific (all the RAN ones), but the point is that adding a quad pom-pom either means removing the only TTs or reducing gun power by 25%. The solution was to swap a 4.7in twin for a 4in twin. The last Canadian built Tribals had 6 x 4.7 and 2 x 4in, as did all the wartime Tribals, and unlike the Porters' 5in they could use their 4.7in in controlled fire, giving them a heavy AA armament.

I am sorry but you are wrong.
a) The last two canadian Tribals had 8 x 4in
b) The Porters did have a combined HA/LA director even though the guns were single purpose like the Tribals
c) Like the Tribals the Porters had a heavy AA gun installed, a single 5in DP in the Porter a twin 4in in the Tribals
d) I certainly agree that the Tribal 4.7 could be used against torpedo bombers and in theory dive bombers after they had dropped their bombsbut against any other kind of air attack they were useless
e) Your theory about the addition of another quad 2pd is I think also wrong. During the war the Australian Tribals were equipped with an addition 6 x 40mm gun which weighed a lot more than one additional quad 2pd
f) If you could supply any evidence to support your theory that the 4.7in was dual purpose I would be very interested to see it. I would also be interested in seeing any evidence that the installation of the 4in was anything to do with weight
Its only fair that I give you my opening support. Its a link to a very well respected website on Naval Weapons. Britain 4.7"/45 (12 cm) QF Mark IX
Please note the opening statement
The lack of a DP function for these weapons was keenly felt throughout the war as more British destroyers were sunk by air attack than from any other cause. What little AA capability that these weapons did have was hindered by a lack of a tachymetric (predictive) fire control system and the setting of HE time fuzes by hand. The last single mounting designed, the CPXXII, had a spring operated rammer, but all other single mountings were completely hand worked. The twin mounting had power ramming and used power training and elevation but no RPC gear was installed.

 

[RCAFson]

I meant the last wartime built Canadian Tribal - my mistake.

 

[RCAFson]

I
b) The Porters did have a combined HA/LA director even though the guns were single purpose like the Tribals
c) Like the Tribals the Porters had a heavy AA gun installed, a single 5in DP in the Porter a twin 4in in the Tribals
d) I certainly agree that the Tribal 4.7 could be used against torpedo bombers and in theory dive bombers after they had dropped their bombsbut against any other kind of air attack they were useless
e) Your theory about the addition of another quad 2pd is I think also wrong. During the war the Australian Tribals were equipped with an addition 6 x 40mm gun which weighed a lot more than one additional quad 2pd
f) If you could supply any evidence to support your theory that the 4.7in was dual purpose I would be very interested to see it. I would also be interested in seeing any evidence that the installation of the 4in was anything to do with weight
Its only fair that I give you my opening support. Its a link to a very well respected website on Naval Weapons. Britain 4.7"/45 (12 cm) QF Mark IX
Please note the opening statement
The lack of a DP function for these weapons was keenly felt throughout the war as more British destroyers were sunk by air attack than from any other cause. What little AA capability that these weapons did have was hindered by a lack of a tachymetric (predictive) fire control system and the setting of HE time fuzes by hand. The last single mounting designed, the CPXXII, had a spring operated rammer, but all other single mountings were completely hand worked. The twin mounting had power ramming and used power training and elevation but no RPC gear was installed.

B)The Porter/Somers class, as built, had a LA only Mk 35 director with no AA capability - see Friedman's The U. S. Destroyers: An Illustrated Design History, p87.

C

D: Here's the engagement envelope of the 4.7in twin:

The level bombers that attacked HMS Prince of Wales and USS Hornet flew at 9000ft and you can see that a 4.7in Tribal-JKM destroyer could have engaged them continuously, if placed on a screen around the ships being attacked. Dive bombers could be engaged prior to dropping their bombs and during their bomb run via barrage placed over the ship being attacked. A barrage, in naval terms, is created by firing the guns with a fuze setting designed to burst at a fixed point in front of the attacking aircraft's path.

e) The Australian tribals retained 8 main guns, their quad pom-pom and their TTs. They didn't reduce their gun armament. In 1940/41 the RN didn't have the option to fit single Bofors guns.

f) Naval weapons of WW2, p50 shows the fuze receiver on the 4.7in twin mount along with the fuze setting pedestal - just as the schematic states in my earlier post; so it has on mount fuze receiver/setter, and it is controlled by an AA FC computer, which in turn was fed data by a HA director - I have pointed this out and supplied hard data via solid references to back it up and it's time you simply admit that it was a DP mounting.

I don't give a hoot for Navweaps editorial comments. It was a DP gun controlled via an AA FC computer. Navweaps is simply wrong. I've already given examples of 4.7in guns being used against aircraft while being controlled by the AA computer but here's a drawing and photo of the mount showing the AA fuze setter:

I earlier pointed out that Lundstrom's two volume study the USN in the Pacific, First Team, hi-lights the poor showing of USN AA was during 1942, so it seems that the USN simply wasted a lot of weight and money on AA systems that seem advanced, on paper, but as per Maury's experience, just weren't very effective:

The performance of the 5" A.A. batteries was uniformly poor. There was much wild shooting with no indication of control other than local. Bursts were in most cases short and ineffective. Other than noise effect on morale it may be assumed that this battery was useless for close range melee.The automatic weapons, 1.1 and 20 m.m. although extremely wild were more effective. At least 85% of the fire observed from these weapons was low and trailing. Failure to lead sufficiently and following the tangent of the tracer trajectory were all too apparent. The only solution is believed to be more practice firing from all angles at high speed towed sleeves. Pointers for 20 m.m. guns should be able-bodied, intelligent, marines, trained in "Duck Shooting."
HyperWar: Battle of Coral Sea--Task Unit 17.2.2 Action Report

I'll bet the above Admiral's comments will never appear on Navweaps or this recommendation from Yorktown after Midway:

(e) Replacement of 5"38 caliber guns, 1.1" guns and 50 caliber machine guns, by a large number of 40mm automatic guns. While smaller caliber automatic guns have proven effective at short ranges, their range is too short to offer effective opposition to attacking planes prior to delivery of their attack. 5"38 caliber guns are very effective at long ranges and should be retained in ships which are used as anti-aircraft screening vessels.
Battle of Midway: USS Yorktown Action Report

 

[RCAFson]

duplicate